Readfile returns 一个空文件

Question

我有强制下载的代码，$file 是现有 .jpg、.png 或 .pdf 文件的 url（我确保它存在）

 <?php
    $file = $_REQUEST['file'];
    $file_extension = end(explode('.', $file));
    $file_name = end(explode('/', $file));
    switch ($file_extension) {
        case 'jpg':
            header('Content-Type: image/jpeg');
            header('Content-Disposition: attachment; filename='.$file_name);
            header('Pragma: no-cache');
            readfile($file);
            break;
        case 'png':
            header('Content-Type: image/png');
            header('Content-Disposition: attachment; filename='.$file_name);
            header('Pragma: no-cache');
            readfile($file);
            break;
        case 'pdf':
            header('Content-Type: application/pdf');
            header('Content-Disposition: attachment; filename='.$file_name);
            header('Pragma: no-cache');
            readfile($file);
            break;
    }

但它正在下载一个空 (0KB) 文件（名称正确）

想过会发生什么吗？

Answer 1

那是因为你少了一个 Content-Length header.

试试这个：

$file = $_REQUEST['file'];
$file_extension = end(explode('.', $file));
$file_name = end(explode('/', $file));

switch ($file_extension) {
    case 'jpg':
        header('Content-Type: image/jpeg');
        break;
    case 'png':
        header('Content-Type: image/png');
        header('Content-Disposition: attachment; filename='.$file_name);
        break;
    case 'pdf':
        header('Content-Type: application/pdf');
        break;
}

header('Content-Disposition: attachment; filename='.$file_name);
header('Pragma: no-cache');
header('Content-Length: ' . filesize($file));

// You may want to add this headers too (If you don't want the download to be resumable - I think).
header('Expires: 0');
header('Cache-Control: must-revalidate');

// And you may consider flushing the system's output buffer if implicit_flush is turned on in php.ini.
flush();

// If you have the file locally.
readfile($file);

// Otherwise,
echo file_get_contents($file); // You should have allow_url_include on in php.ini

还没来得及尝试，但应该可以。

Answer 2

由于 file_get_contents() return 也为 null，您的问题可能是 php.ini 配置中的设置。

参数allow_url_fopen必须On.

Readfile returns 一个空文件

Readfile returns an empty file

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file

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readfile